Multiple sclerosis (MS) is a disease characterized by myelin destruction, which is probably caused by T cells which are specific for an unknown myelin antigen. When these cells are exposed to an altered form of the myelin basic protein (MBP) peptide, they are deactivated. The immunologically dominant portion of MBP in humans has been identified, and an altered form of this peptide, NBI-5788 has a regulatory effect on human MBP-specific T cells in culture. This is the first study of this peptide in humans, and will test safety and an optimum dose.